Engine starter drive



March 16, 1954 J. J. DIGBY 2,672,055

ENGINE STARTER DRIVE Filed July 16, 1952 as 14 32 55 5F on llll Ill IHIN hmh Illi"" IN VEN TOR.

OBNE Y WITNESS:

Patented Mar. 16, 1954 2,672,055 ENGINE STARTER DRIVE James J. Digby, Elmira, N. Y., assignor to Bendix Aviation Corporation, a corporation of Dela- Ware Application July 16, 1952, Serial No. 299,085

The present invention relates to a heavy duty engine starter drive and more particularly to a self-contained drive unit which is attachable to the shaft of a starting motor for making connection with an engine gear and for maintaining said connection until the engine is reliably self-operative.

It is an object of the present invention to provide a novel engine starter drive which is adapted to transmit heavier loads than those customarily transmitted by drives of comparable size, and which is so formed as to maintain the proper location and alignment of its parts in spite of the application of such heavy torque loads.

It is another object to provide such a device incorporating a self-tightening overrunning clutch connection to the drive pinion, and a centrifugally released detent on the pinion for holding it meshed with an engine gear until the engine has attained a predetermined rotational speed.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partially broken away and in section of a drive forming a preferred embodiment of the invention, showing the parts in idle position;

Fig. 2 is a similar view showing the parts in cranking position; and

Fig. 3 is a section taken substantially on the line 33 of Fig. 1.

In Fig. 1 of the drawing there is illustrated a shaft I having a socket 2 in one end adapted to receive the end of the armature shaft 3 of a starting motor, not illustrated. Means in the form of key members 4 and set screw 5 are provided for rigidly connecting said shaft I to the motor armature shaft 3.

Shaft I is formed with flat surfaces 6 and I on which a driving anchor plate 8 is non-rotatably mounted, said anchor plate being retained on the shaft by a terminal flange 9.

Shaft I is provided with a smooth reduced extension II forming a shoulder I2 adjacent which a driven anchor plate I3 is slidably and rotatably mounted, its movement away from said shoulder being limited by a stop ring III seated in a groove in said shaft. A drive spring I5 forms a yielding driving connection between the anchor plates 8 and I3 by virtue of out-turned ends I6, II of the spring which enter corresponding slots in the anchor members. Lock ring I4 so positions the anchor plate I3 as to maintain spring I5 6 Claims. (01. 74-7) under a slight initial compression. The cornpression of spring I5 is limited by the shoulder l2 on the shaft I which provides an abutment for the anchor plate l3.

A screw shaft I8 is slidably journaled on the extension I I of shaft I, and is provided with overrunning clutch teeth I9 which are adapted to cooperate with similar teeth 2| on the anchor plate I3. A stop member 22 is located on the smooth portion II of shaft I, and a light thrust spring 23 and washer 24 which are interposed between said stop member and the adjacent end of screw shaft I8 yieldingly hold the overrunning clutch teeth in engagement.

A pinion 25 is threaded on the screw shaft I8 for movement into and out of engagement with a gear 26 of an engine to be started, its meshing movement being limited by the stop member 22. A detent 21 is mounted for radial sliding movement in a flange 28 forming part of the pinion 25, and is pressed against the screw shaft I8 by a spring 29 which is positioned by suitable means such as a screw plug 3|. Screw shaft I8 has an inclined shoulder 32 in position to be engaged by the detent 2'! to yieldingly resist initial meshing movement of the pinion. Said screw shaft is also provided with a radial shoulder 33 so positioned that the detent 21 drops down back of said shoulder as the pinion approaches its fully meshed position, whereby the demeshing movement of the pinion is prevented by engagement of the detent with the shoulder 33 until the pinion is rotating at sufficient speed to withdraw the detent 21 by centrifugal force.

The outer end of the smooth portion II of shaft I is preferably supported by means of an outboard bearing 34 which may be mounted on the starting motor frame in any suitable manner.

In operation, starting with the parts in the positions shown in Fig. l, rotation of the starting motor shaft 3 is transmitted through anchor plate 8, spring I5, and anchor plate I3 to the screw shaft I8 by means of the clutch teeth 2|, I3. The consequent acceleration of the screw shaft traverses the pinion 25 into mesh with the engine gear 26, and when the movement of the pinion is arrested by the stop member 22, the screw-jack action of the screw shaft and nut forces the screw shaft backward against the anchor plate I3, compressing the drive spring I5 until the movement of said anchor plate is arrested by the shoulder I2 on shaft I. The over running clutch teeth 2|, I9 are thus forced tightly together during the subsequent cranking operation.

When the engine starts, the acceleration of the pinion 25 by the engine gear 26 moves the pinion back on the screw shaft until the detent 21 engages the shoulder 33. At this time, the pressure of the screw shaft I8 against the anchor plate [3 is relieved, except for the slight amount produced by the clutch spring 23. The pinion and screw shaft can thus overrun the anchor plate !3 freely Without transmitting torque back to the motor shaft 3.

If the engine should not remain self-operative, as soon as the speed of the starting motor exceeds that of the pinion and screw shaft, th cranking operation will be resumed. When, however, the engine has become reliably self-operative as evidenced by the rotation of the pinion 25 by the engine gear above a predetermined speed, the detent 2! is withdrawn from the shoulder 33 by centrifugal force and the pinion is then returned to idle position by overrunning the screw shaft, rebounding toward meshing position being prevented by the engagement of the detent 21 with. the inclined shoulder 32 on the screw shaft when the excessive rotational speed of the pinion is arrested as the pinion arrives at its idle position.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and that changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. In an engine starter drive, a shaft having a socket at one end and a smooth reduced extension beyond the socket forming a circumferential shoulder, a driving anchor plate fixedly mounted on the socket end of said shaft, a second anchor plate slidably and rotatably mounted on the reduced portion of the shaft adjacent said shoulder, a torsion and compression spring connecting said anchor plates, a screw shaft slidably journaled on said reduced portion, having an overrunning clutch connection to the second anchor plate, a pinion having a threaded connection with the screw shaft for movement into and out of mesh with a gear of the engine to be started, and a stop member fixed on said reduced portion of the shaft, defining the operative position of the pinion.

2. An engine starter drive as set forth in claim 1 in which the adjacent surfaces of the second anchor plate and the screw shaft are provided with cooperating overrunning clutch teeth which are clamped together between the shoulder and the stop member on the shaft by the screw-jack action of the screw shaft during the cranking operation.

3. An engine starter drive as set forth in claim 2 including further means on the smooth portion of the shaft for limiting the movement of the second anchor member away from said shoulder.

4. A starter drive as set forth in claim 3 including further compression spring on said shaft between the stop member and the adjacent end of the screw shaft yieldably holding the overrunning clutch teeth in engagement.

5. A starter drive as set forth in claim 1 including further a detent in the pinion bearing on the surface of the screw shaft, said screw shaft having a shoulder positioned to engage the detent and resist demeshing' movement of the pinion.

6. A starter drive as set forth in claim 5 in which the screw shaft has an inclined shoulder positioned to engage the detent and resist initial movement of the pinion away from idle position.

JAMES J. DIGBY.

No references cited. 

